2021 Volume 34 Issue 3 Pages 263-269
Triggered by the notable evolution of organic-inorganic metal halide perovskite solar cells (PSCs) with three-dimensional (3D) ABX3 (A: organic/inorganic cation, B: metal cation, X: halogen anion) structures, Ruddlesden-Popper two-dimensional (2D) pseudo perovskites given by An+1BnX3n+1 (n = 1, 2, …) are also becoming a material of interest, as they exhibit improved stability against moisture and oxygen. Controlling the crystallographic orientation of these 2D layers plays a key role in the power conversion efficiency (PCE) of PSCs and their environmental tolerance. Here, we report the effect of top thermal annealing (TTA) on the PSC photoconductivity and performance, where TTA is a process that exposes heat from the top side (rather than the bottom (substrate) side in normal annealing) to form the perovskite layer after anti-solvent treatment. The anisotropic photoconductivity in the in-plane and out-of-plane directions was evaluated, which suggested a vertical gradient of 2D/3D phases with a 3D-rich component on the surface.
